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PCI/I-P54SP4
User's ·Manual
Upgrading System Memory
This section explains how to install more system memory. There
are instructions on how to configure and install memory and an ex-
planation of the technical specifications required.
System DRAM is the main source of data for the CPU. Data re-
mains stored in DRAM as long as the system is turned on, and is lost
when you tum
it
off. The Level 2 cache memory is Static RAM
(SRAM), which is faster than DRAM memory. When the CPU looks
· for data, it first searches the cache.
If
the information is not there, the
search continues in the DRAM. With this design, the CPU looks in
the fastest source of data first, which lets it operate as fast as possible.
The DRAM subsystem uses memory chips permanently mounted
on small circuit boards to form "SIMMs" (Single In-line Memory
Modules). The memory chips have a speed rating that is measured
in nanoseconds (ns ). This mainboard requires fast page mode DRAM
with a speed of at least 70ns.
This mainboard can use 72-pin SIMMs in six sizes from 1MB up
to 32MB (megabytes). Depending on the combination of modules you
use, you can install between 2MB and128MB. The 32-bit modules
used for this board come with memory chips on either one or both
sides of the module.
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2-6
Upgrade Guide
Configuring System Memory
If
you want to add system memory, you must use the configura-
tion options and specifications shown in this section.
Memory Combinations
You can configure the system memory in a variety of ways, us-
ing different combinations of SIMM modules. Using the 4 SIMM
sockets there are many configuration options.
The chart on the next page shows the supported combinations.
The only restrictions are:
• You must use 2 sockets at a time, in sequence, i.e. SIMMl and
SIMM 2, or all four sockets at once.
• Each pair of modules must be the same size and speed and
can be either single or double-sided.
• You must set the RNll/12 resistor position to indicate
whether single or double-sided SIMMs are installed in sock-
ets! and 2.
• Memory Specifications:
Module Size:
Single-sided SIMMS: 1MB, 4MB, 16MB
Double. , - sided SIMMS: 2MB, 8MB, 32MB
DRAM Mode: Fast Page Mode
DRAM Speed: 70ns (or faster)
RAS access time [Trac]: 60ns- 70ns
CAS access time [Tcac]: 10ns- 25ns
Parity: Either parity or non-parity
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2-7
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